Clamping circular objects with a pair of opposing jaws is known in the art, for example in U.S. Pat. No. 5,201,501 to Fassler. However Fassler relies upon a three point contact, and uses springs which are aligned along an axis different from the clamping force.
U.S. Pat. No. 5,513,838 to Van Rossum teaches a method using a partially circular ring with multiple threaded clamps, to apply pressure to the perimeter of an object. However the force on the object depends on the force resulting from the torque applied to the threaded clamps.
U.S. Pat. No. 3,661,409 to Brown teaches a circumferential clamping device having chain links with wedges to aid in the drawing together of pipe coupling sections. The device is tightened by turning a threaded shaft and does not include compression springs.